Lecture 9 BIO 311D 2nd Edition Outline of Last Lecture I Multiple selection factors working at once including heterozygote advantage II Evolution occurs in populations over time Outline of Current Lecture I Different Definitions of Species II How do new species form Current Lecture I Different definitions of species A Review Macroevolution new species are formed Galapagos Finches serve as an example for microevolution and macroevolution Microevolution change in beak size Macroevolution adaptations adaptive radiation B What s a species How do we know when it is a new species Morphological Species Concept based on morphological structural traits Fossil analysis is possible Used by Linnaeus to devise the species naming and classification system Species are independent evolutionary units Biological species concept groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups Disadvantages doesn t account for asexual organisms fossil analysis aren t possible you can t walk through an environment and notice new species through the biological species concept The study of bacterial species asexual reproduction bacteria can exchange genes through the plasma therefore should be studied through the morphological species concept combined with biochemical views II How do new species form A Process of speciation requires genetic divergence and reproductive isolation 1 Genetic divergence how fat apart are they from one another Lack of gene flow non random mating mutations genetic drift sexual selection etc B Not all evolutionary changes result in new species A species may change without giving rise to a new species or may transform into a new species A speciation results from one species splitting into two species each of which involves as a distinct lineage C Modes of speciation 1 Allopatric divided by geographic barrier 2 Populations are separated Lead to genetic divergence Sympatric speciation without geographic barrier Populations are together Diverge genetically Mutations that multiplies the chromosomes a polyploidy event a genetic divergence that could possibly cause an instant reproductive isolation this is more common in plants
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